More than 100 people are out of work in Tilbury.
Worthington Cylinders announced on Tuesday it will close its factory there.
The plant makes high-pressure gas containers for the welding and beverage industries.
Employees were told at a staff meeting the plant will close in January.
Sonya Higginbotham, who speaks for the company, said Worthington is getting out of the cylinder business because it's not profitable.
"This was a very difficult decision especially when people are impacted. So we did everything we could do and we will do everything we can to help them find future employment," she said.
Higginbotham said employees losing their jobs will be offered other positions in the company but those are "mainly U.S.-based."
"We do have open positions," Higginbotham said.
The company is still working with the union to develop severance packages for those who do not accept or get positions elsewhere.
Jesse Walker, a spokesperson for the mostly unionized workforce, said the announcement came as a complete shock, and it was more upsetting because it's so close to Christmas.
Walker anticipated the announcement was going to be that the company acquired another company.
"There are some people very upset and others didn't know what to say one way or another," Walker said."The hope was a happy announcement rather than negative."
Walker said employees commuted from as far away as Chatham and Windsor.
"It's a heavy, heavy blow for Tilbury," Walker said. "It's going to be devastating for the town and neighbouring communities."